The biological function of various methylated nucleosides present in the nucleic acids of tumor cells and DNA- and RNA-viruses will be investigated by appropriate immunochemical techniques. Antibodies, specific for such methylated constituents as N6-methyladenosine (m6A), 7-methylguanosine (m7G) and 5-methylcytosine (m5C) will be prepared, extensively purified and employed to characterize those nucleic acids possessing the corresponding antigenic haptens. Nucleic acid of particular interest include Adenovirus DNA and mRNAs and RSV-RNA and ASV-RNA. The interaction between nucleic acids and antibodies (of the type described above) will permit the detection of methylated constituents on nucleic acids (immunospecific precipitation and/or retardation), localization of methylated nucleosides (electron micrographs of nucleic acid-antibody complexes), and isolation of specific oligonucleotides adjacent to methylated constituents for subsequent sequencing data. In addition, the inhibition of specific enzyme activities associated with the metabolism of nucleic acids, by the appropriate nucleic acid-antibody complex, will provide information as to the functional role(s) of methylated nucleosides.